Furnace construction



C. M. JOHNSON.

FURNACE CONSTRUCTION.

APPLICATION FILED NOV. 19, I919.

Patented Feb. 3, 1920.

FIG.Z-

INVENTOR WITNESSES UNITED STATES PATENT OFFICE.

CHARLES MORRIS JOHNSON, 0F AVALON, PENNSYLVANIA.

FURNACE CONSTRUCTION.

Specification of Letters Patent.

Patented Feb. 3, 1920.

Application filed November 19, 1919. Serial No, 339,236.

To'aZZ whom it may concern Be it known that .1, CHARLES MORRIS Jonxsox, residing at Avalon, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in Furnace Construction, of-

Which improvements the following is a specification.

My invention relates to the sealing of furnace chambers, and particularly chambers wherein a non-oxidizing atmosphere is to be maintained; and, since the difficulty in maintenance of an atmosphere of this character is peculiarly acute in continuous furnaces, where the charge is carried in and out while the processes accomplished are going on uninterruptedly within the chamber, my invention finds its chief and immediate application in continuous furnaces. But it is not limited, in its application, to continuous furnaces, nor even to metallurgical furnaces although it is chiefly in the field of metallurgy that closed chambers containing nonoxidizing atmosphere maintained at high temperature are employed.

It is common in continuous furnace structure to seal the edges of moving parts with some inert mobile material, in order to cut off ingress of air. It is common to use dry sand as a. sealing material; but such a seal is imperfect; some air percolates through the seal; and, besides, the sand, escaping from its container, is often a source of. annoyance and difiiculty, working between conveyers opening air spaces, and causing wear I of parts.

My invention in broadest aspect consists in employing a carbonaceous material, as distinguished from an inert material,a material which under the conditions obtaining in service has avidity for oxygen.a substance which burns; and which, combining, by burning, with such oxygen as otherwise would peroolate through the seal, renders the so modified air, gaining access to the furnace chamber, non-oxidizing. It may even be reducing. As to the combustion and consequent consumption of the sealing material, it is a relatively slow process, for the quantities of air which gain ingress are small, and the material used may be augmented with new supplies from time to time, and the seal so maintained will meet the needs of practice I do not limit myself to any particular reducing material, but manifestly a carbonaceous materialis referable, if only on the score of cost; ant, of carbonaceous materials, I have found coke dust to suit my purposes well. The coke dust I employ is preferably screened, in preparation for use, through a 15-to-the-inch screen, or thereabout. Coke dust I find is not objectionable as sand iswhen itescapes from its con- .tainer. For, unlike sand, particles of coke are readily crushed still finer by pressure and so coke does not, as sand does, lodge between c-onveyers and open-air spaces 'between them, but rather whatever finely crushed coke ma) lodge between containers will act upon whatever air might otherwise find ingress, after the same manner in which it acts in the sealing trough. That is to say, it will combine with oxygen and so prevent bad results, Furthermore, particles of coke will not. abrade as do particles of sand. The effect in steel heating furnaces is to keep down scale loss. In high speed steel much valuable timgsten is lost by scaling in present-day operations.

I shall, for purposes of illustration, now describe my invention in application to a reduction furnace-a furnace such as I have found useful for the reduction of tungsten ore.but I do not mean to limit myself to such a furnace. nor even to a reduction furnace: manifestly, the invention is applicable to annealing furnaces as well, and indeed it is applicable to the sealing of any chamber for any purpose, where there is the possibility that air may have access and within which a non-oxidizing atmosphere is to be maintained.

Referring to the drawings, Figure I is a. view in transverse vertical section of a furnace of a kind known as the Bailey electric furnace, this being a furnace. which I have found suitable for the reduction of tungsten ore. My invention is applied to this furnace as presently will be explained. Fig. II is a similar view through th cooling chamber of the same furnace. Fig. III is a view in horizontal section through the furnace. In Fig. III the. planes of section of Figs. I and II are indicated by the lines II and IIII, respectively, and in Figs. I and II, the plane of section of Fig. III is indicated by the lines IIIIII.

The furnace includes the heating chamber proper 1, and the continuation of'it in the cooling chamber 2. It is a continuousfurnace, and, accordingly, Fig. III indicates that both portions are of indefinite extent and that they are intercommunicating. Conveniently, a succession of cars 3, traveling on rails 4 carries the char e through the fur- .nace, advancing in the cirection indicated by the arrow at (Fig. III), that is, in the dire: tion from the heating chamber to the cooling chamber.

The characteristic of the Bailey furnace is that it is heated by an electric current traversing a mass of broken or granular car-' bon. The preferred arrangement is shown sides the cars are provided with troughs, 6,

and into these troughs aprons 7 depend. Sealing is afforded by a suitable sealmg material contained in these troughs and covering the depending edges of aprons 7. Beyond the heating-chamber, the depending edges of the cooling chamber (which is merely a screen arched over the plat-forms of the cars and covering theirload) take the place of aprons '4' and continue the'seal. It will be seen that the succession of cars, abutting closely one against another, complete a substantially continuous partition across the furnace chamber, limiting the heating region to the space above the cars and protecting the running gear from undesired high temperatures. The car platform, exposed as it is to high temperature, is shown to be faced with fire brick. The leakage to be guarded against is through this partition, made up as it is )artly of stationary, partly of moving, mem ers, and it is at the point of union of station with movable members that the seal is provided. The sealing substance here employed, and in which my invention consists is a granular oxidizable substance, ordinarily carbonaceous, and preferably coke. The furnace chamber then is, as a matter of fact, not the whole space within the masonry, as indicated in Fig. l, but only so much of that space as lies above the partition formed by troughs 5, car 6, and flanges 7.

The Bailey furnace used as I use it, for reducing tungsten ore must be operated at higher temperature. than when used as an annealing furnace. I have made no experiments, to determine the limits of temperature under which my invention may be enjoyed; but it will be apparent that, wherever the temperature is great enough to bring the granular sealing material to a point at which it will combine with the oxygen of such quantities of air as percolate through, and by so combining will mitigate or eradicate the bad effects otherwise consequent upon the ingress of air, my invention is realized. In point of fact, under the conditions which obtain in my practice now described, the heat is such in intensityand the quantity of air seeking entrance is so small and its movement so slow that the gas which actually enters the furnace chamber is largely carbon monoxid, a reducing gas.

The drawings show the furnace charge to be a quantity of cylindrical cases, or capsules. These were adopted for my particular metallurgical operation (the reduction of tungsten ore) after I had, procured a Bailey furnace for the purpose, but before I had made my invention. I thenfound the entering air to interfere with and measurably to defeat the reduction intended, and it was to protect the furnace charge against air while still subjecting it to the temperature generated, that I inc-losed it in such capsules. Such protection was adequate, but the air which gained access still, under the elevated temperature, attacked the sub stance ofthe capsules, so that they were very short-lived. My invention followed. Employing it, destruction of the capsules is eliminated, and, more than that, I find it no longer necessary to inclose the charge in tight capsules; it may lie in troughs or boats, exposed to heat radiation from the reverberatory roof. I show the capsules, however, to aid in an understanding of the invention.

I claim'as my invention:

1. A seal for the meeting edges of the walls of a heated chamber consisting of abody of granular material having avidity for oxygen.

' of material having avidity for oxygen.

In testimony whereof I have hereunto set my hand.

CHARLES MORRIS JOHNSON.

Witnesses:

BAYARD H. CHRISTY, FRANCIS J. TOMASSON. 

